One of the problems with the current technology for drug delivery is the lack of precision and resulting lack of quality control. This in turn causes a lack of precision in the release rates of the encapsulated drug and requires that patients take the drug at specified times throughout the day. Oftentimes, especially for complex dosage regimes, patient compliance is well below acceptable levels, resulting in diminished therapeutic effect. Construction of drug delivery devices which could release drugs according to complex prescribed temporal patterns could have broad application for delivery of bioeffecting agents by both oral and implantable routes. For example, implants to areas of the body not easily accessed, such as the ocular cavity, can be designed for prolonged drug delivery. Dosage forms in which release of active coincides with circadian rythms are also possible. In addition, patient compliance problems can be obviated by reducing the number of times a patient must self administer drug.
U.S. Pat. No. 5,490,962 teaches the preparation of dosage forms using solid free-form fabrication (SFF) methods. These methods can be adapted for use with a variety of different materials to create dosage forms with defined compositions, strengths, and densities, through the use of computer aided design (CAD). Examples of SFF methods include stereo-lithography (SLA), selective laser sintering (SLS), ballistic particle manufacturing (BPM), fusion deposition modeling (FDM), and three dimensional printing (3DP) to precisely position bioactive agents(s) within a release matrix to control the rate of release and allow either a pulsed or constant release profile.
The macrostructure and porosity of the dosage forms of the '962 patent can be manipulated by controlling printing parameters, the type of polymer and particles size, as well as the solvent and/or binder. Porosity of the matrix walls, as well as the matrix per se, can be manipulated using SFF methods, especially 3DP. Structural elements that maintain the integrity of the devices during erosion can also be incorporated so that more linear release of incorporated material is obtained. Most importantly, these features can be designed and tailored using computer aided design (CAD) for individual patients to optimize drug therapy.
Despite the significant advances in drug delivery systems (DDS) described by U.S. Pat. No. 5,490,962, there is room for improvement implementing 3DP to produce suitable dosage forms. For example, the treatment of various disorders with multiple drug therapy may require different release rates for each drug. A single dosage form combining the multiple drugs would require separate domains for drug release at the different rates. Drugs having high potency and/or toxicity require special handling for both safety reasons and consistency in dose level. Other drugs may have low solubility in bodily fluids, requiring that they be modified for proper absorption. Certain drug therapies may require pulsatile release over prolonged periods.
The present invention addresses these needs.